Anyone who teaches MT can make up a black belt and if someone works hard and gets it, then their student has a black belt in MT. If the one true Scotsman tell him that he doesn't respect his public accolade and that real MT doesn't have belts, he is welcome to his opinion, but to me, his opinion doesn't mean anything.
Martial artists get belts. MT is a martial art. MT should have belts. If an MT instructor makes up a belt system, it is just as genuine as every other belt system. It means the same.
Belts don't mean anything to me. I've never cared about testing for belts anywhere I've trained sense I've been an adult. The only ranks I have are in Kali and Silat, and I didn't ask for them. I was handed them, probably so I could teach class.
But if someone tells me they are 6 and 1 in MT or a 3rd degree black belt in MT, both mean the same to me - jack shit. I'll decide what I think of you after we spar. If we don't spar, I'm happy to act like I believe anything you tell me about yourself.
What I find silly is supposedly serious martial artists caring about someone getting a belt in a martial art. Belts are for people just beginning their martial arts journey. They are obviously stupid. They don't usually reflect much skill and the reason is because most people don't get good in 2-5 years. They get ok. 10 years later when they are actually sweet, they have probably graduated to big boy thinking and think hashing out who is what rank isn't important to them. Once you are all grown up in the martial arts, you only care about learning or having a good time sparring or competing. Worrying about who is what rank is for bored lineage police, people that like to role play samurai, and people just starting martial arts.